export default{
  bind(el, binding, vnode) {
    const { dragDom = '.el-dialog', dialogHeaderEl = '.el-dialog__header' } = binding.value
    const $dialogHeaderEl = el.querySelector(dialogHeaderEl)
    const $dragDom = el.querySelector(dragDom)
    console.log(dragDom)
    $dialogHeaderEl.style.cssText += ';cursor:move;'
    $dragDom.style.cssText += ';top:0px;'

    // 获取原有属性 ie dom元素.currentStyle 火狐谷歌 window.getComputedStyle(dom元素, null);
    const getStyle = (function() {
      if (window.document.currentStyle) {
        return (dom, attr) => dom.currentStyle[attr]
      } else {
        return (dom, attr) => getComputedStyle(dom, false)[attr]
      }
    })()

    $dialogHeaderEl.onmousedown = (e) => {
      // 鼠标按下，计算当前元素距离可视区的距离
      const disX = e.clientX - $dialogHeaderEl.offsetLeft
      const disY = e.clientY - $dialogHeaderEl.offsetTop

      const $dragDomWidth = $dragDom.offsetWidth
      const $dragDomHeight = $dragDom.offsetHeight

      const screenWidth = document.body.clientWidth
      const screenHeight = document.body.clientHeight

      const min$dragDomLeft = $dragDom.offsetLeft
      const max$dragDomLeft = screenWidth - $dragDom.offsetLeft - $dragDomWidth

      const min$dragDomTop = $dragDom.offsetTop
      const max$dragDomTop = screenHeight - $dragDom.offsetTop - $dragDomHeight

      // 获取到的值带px 正则匹配替换
      let styL = getStyle($dragDom, 'left')
      let styT = getStyle($dragDom, 'top')

      if (styL.includes('%')) {
        styL = +document.body.clientWidth * (+styL.replace(/\%/g, '') / 100)
        styT = +document.body.clientHeight * (+styT.replace(/\%/g, '') / 100)
      } else {
        styL = +styL.replace(/\px/g, '')
        styT = +styT.replace(/\px/g, '')
      }

      document.onmousemove = function(e) {
        // 通过事件委托，计算移动的距离
        let left = e.clientX - disX
        let top = e.clientY - disY

        // 边界处理
        if (-(left) > min$dragDomLeft) {
          left = -min$dragDomLeft
        } else if (left > max$dragDomLeft) {
          left = max$dragDomLeft
        }

        if (-(top) > min$dragDomTop) {
          top = -min$dragDomTop
        } else if (top > max$dragDomTop) {
          top = max$dragDomTop
        }

        // 移动当前元素
        $dragDom.style.cssText += `;left:${left + styL}px;top:${top + styT}px;`

        // emit onDrag event
        vnode.child.$emit('dragDialog')
      }

      document.onmouseup = function(e) {
        document.onmousemove = null
        document.onmouseup = null
      }
    }
  }
}
